Pneumatic hammer



Jan. 26, 1943. R. J. CHAMPAYNE 2,309,097

PNEUMATIC HAMMER 2 Sheets-Sheet 1 Filed March 25, 1939 NvsNToL Qog ()7 Cfiampag/rze H Wm, w-n, f' .1]

- (fiTTowEps 1943- R. J. CHAMPAYNE PNEUMATIC HAMMER.

Fiied March 25, 1939 2 Sheets-Sheet 2 5 E 0 W P M W, M Q4 Patented 26, 1 943 UNITED STATES PATENT OFFICE rnnom'ncnamvmn 7 Roy J. Ohampayne, Rockford, Ill. Application March 25, 1939, Serial No. 264,067

6 Claims. (o1. 153-32) I tions falling within the spirit and scope of the This invention relates to pneumatically actuated hammers of the type used for straightening sheet metal parts such as the fenders, bodies, etc. of automotive vehicles.

The general object is to provide such a hammer which is more powerful and efficient in operation, simpler and less expensive in construction and easier and more convenient to control than prior hammers of the same general character.

A more specific object is to provide for raising of the lower die member to and holding the invention as expressed in the appended claims;

The hammer shown by way of illustration comprises generally a yoke ill, a lower ,die member ll mounted on one end of the yoke for vertical movement into engagement with one side of the work piece Wto be operated uponand a head I2 detachably mounted on the other-end of the yoke and having self-contained therein an upper die member 13, a pneumatic actuator therefor, a connection with a source of air pressame inoperative position by pneumatic pressure without detracting from the ease of control or the versatility of th hammer.

.Another object'is to provide for control of the hammer by the operator's thumb while the hammer is gripped by the operator's hand ina convenient position of balance.

A further object is to lubricate the mounting of the lower die member in a novel manner.

Still another object is to provide a novel construction and mounting of the upper di member contributing to the versatility of the hammer.

The invention also resides in the novel manner of coupling the yoke detachably to the pneumatic actuator head and the novel means for closing the upper .end of the actuator of the actuator cylinder.

Other objects and advantages of the invention will become apparent from the following desure and a manually operable control valve.

To adapt the hammer for operation on various types of sheet metal pieces or different locatailed description taken in connection with the accompanying drawings, in which Figure l is a perspective view of a pneumatic hammer embodying the novel features of the present .invention illustrating the manner of .using the hammer in straightening a'fend'er.

, Figs. 2, 3, and 4 are side elevational views of the improved hammer equipped with yokes'of diflerent shapes and with portions of the yoke shown in section.

Fig. 5 is a fragmentary diametrical cross sectional view of the improved hammer with the central portion of the yoke broken away.

Fig.6 is a fragmentary perspective view of part of the hammer head.

Fig. 7 is a section taken along the line 1-1 of Fig. 5.

While the invention is susceptible of various modifications and altennative constructions, I

have shown in the drawings and will herein describe in detail the preferred embodiment. It is to be understood that I do not thereby intend to limit the invention by such disclosure, but aim to cover all modifications and alternative construc tions on a vehicle body, various sizes and shapes of yokes may be employed as shown in Figs. 2, 3, and 4. Each of these yokes is substantially G- shaped, being bent intermediate its ends to form generally parallel opposite end portions or arms l4 and IS. The arm H is substantially straight clear-to its end while the arm l5'preferably is bent as indicated at l6 near its end to-form a short end II the axis of which is disposed at right angles to the axis of the am It and intersects the latter axis a short distance beyond the end of the arm 14. By virtue of the bend- I6, the

yoke is of greater effective. width adjacent its ends, thereby contributing to the versatility of application of the hammer to various kinds of work.

In the present instance, the lower die member I3 is raised into contact with the work by air pressure and constitutes a yieldable backing for supporting the work from its under side when each blow is struck bythe upper die member. I For this purpose, a sleeve [8 screw threaded onto the end I! cooperates .with the latter to form a cylinder IS in which a piston 20 reciprocates freely. A leather washer 2! is attached to the lower end of'the piston to minimize leakage and to facilitate lubrication of the piston in a manner to be described later. I

- The piston projects from the cylinder and its reduced upper end 22 is received in a socket 233- I on the under side of-the die member II, the

two being held together frictionally by an expansible ring 24 encircling a groove in the end 22. The die member may be detached from the piston and replaced by one having an. upper surface of a contour best suitied to the work piece .to be operated upon.

The invention contemplates utilizing the yoke III to perform the additional function of conducting air under pressure to the lower .end 01' the cylinder is so as to maintain the lower die raised as shown in Fig. during operation of the tool. To this end, the yoke comprises a single piece of seamless steel tubing and, as will appear later, air is admitted to the end I4 of the tube and conducted to the cylinder l9 through the entire length of the tube. The yoke may thus be constructed as a single integral piece without joints or holes therein for admitting the compressed air.

The head I2 is a generally T-shaped tubular casting and comprises a tube 26 and a tubular extension 21 internally machined to receive the end of the straight yoke arm |4, the end abutting against a. gasket 28 backed by a shoulder 29. The yoke and head are fastened together in a novel manner which permits of ready disconnection of the two to interchange yokes or of swiveling of the head aboutthe yoke in applying the tool to certain kinds of work while at the same time insuring against breakage or loosening of the parts under the severe vibration to which the coupling is subjected in service operation. For this purpose, a longitudinally extending slot 30 is formed in the extension 21 and is adapted to receive the squared head 3| of a set screw 32 threaded into the yoke arm M at a point spaced from its end. Ears 33 .cast on the extension on opposite sides of the slot 30 are apertured to receive a bolt 34 which is transversely milled to form a slot 35 that registers with the slot 30 when the bolt is fully entered through the ears and turned to a predetermined angular position.

The arrangement is such that when the yoke end I4 is fully entered and abutting against the gasket 28, the lug 3| will be disposed beyond the axis of the bolt as shown in Fig. 5. By means of a wrench applied to its head, the bolt is turned in a counter-clockwise direction sothat the edge 36, acting on the lug 3|, forces the yoke arm firmly against the gasket. With the parts thus held, a wing nut 31 is tightened thereby contracting the extension 21 around the yoke arm and clamping the two firmly together. loosening the nut, the head |2 may be slipped entirely off from the yoke and applied to another yoke. Or, the head may he slid oil? far enough to permit the head to swivel about the yoke arm I 4.

The lower end of the head tube 26 is machined externally as indicated at 42 to snugly receive a flange 38 on the upper die member l3 which therefore is of cup shape. The cup maybe retained on the tube frictionally as by means of a contractible ring 39 seated in a groove 40 around the flange and having a part projecting through an arcuate slot 4| and bearing against one side of the surface 42. v r

The tube 26 is bored to form two cylinders 43 and 44 in which reciprocates a plunger 45 having two spaced pistons 46 and 41 sliding in the cylinders 43 and 44. .The lower end 48 of the plunger extends-beyond the piston 46 and has a hardened head 49.- which strikes the upper die member as shown-in full lines in Fig. 5 when the plunger isprojected downwardly. This head constitutes an auxiliaryvdie member of smaller size than the main die member l3 and will be projected from the tube 26 and operate directly on the work when the main die cup is removed.

The other end of the plunger 45 has an axial bore '50 communicating with radial passages 5| which terminate in an annular groove 52 on the piston 41. The groove is adapted to register with a wider internal groove 53 in the cylinder After 44 above which an exhaust port 54 is cut through the casting.

The outer end of the cylinder 44 is closed by means including a disk 55 pressed into the counterbored end of the cylinder below a groove 56 in which a ring 51 is expanded. A cap 68 is clamped against the end of the tube by a screw 59 extending through the cap and, threading into .the disk 55 to draw the latter against the ring 51. A fluid tight closure is thus provided which is not subject to loosening or breakage oi the parts under the severe vibration encountered in service use of the hammer. 7

With the plunger lowered as shown in full lines, air under pressure is admitted through a passage 60 to the space between the pistons 46 and 41. Owing to the larger size of the piston 41, the plunger is raised. After the port 54 has been covered and when the piston 41 passes the groove 53, the compressed air flows through the groove 52, the passages 5| and the bore 50 into the space above the piston. Here the pressure builds up rapidly, first cushioning and arresting the upward movement of the plunger without the latter contacting the disk 55. Then, the

compressed air, acting on the upper end of the piston 41, projects the plunger downwardly. I

This continues until the plunger reaches the position shown in full lines at which time the groove 53 is covered and the port 54 is uncovered by the piston 41. As a result, the plunger is reciprocated extremely rapidly imparting a sharp impulse to the die member l3 on each downward stroke. 1

, A hose 60 leading from a source of compressed air is attached to a fitting 6| threaded into a boss 62 on the upper side of the tubular extension 21 beyond the end of the yoke and closely adjacentthe tube 26. Between the fltting and the cylinder 44, the tubular extension 21 is formed with a transverse bore 63 which intersects the passage 60 perpendicular to the plane of the yoke III. A rotary valve member 64 in the form of a cylindrical pin projects through the bore 63 and has a diametrical passage 65 therethrough. With the pin positioned as shown in Fig. 5, the valve is closed. When the member 64 is turned through a small angle in a clockwise direction, the passage 65 is brought into register with the passage 60 permitting air to flow from the hose into the cylinders 43 and 44 and also through a passage 66 into the end l4 of the yoke. The extent of such angular movement determines the amount of air admitted and therefore the speed of, the pneumatic actuator.

The valve is arranged to be actuated and the degree of opening controlled variably and accurately by manipulating the thumb of one of the operator's hands while the hammer is gripped or held by such hand at a'convenient and natural point of balance. For this purpose, a generally L-shaped actuator arm 61 isextended radially into and rigidly attached to the projecting end of the valve member 64, preferably on the left side of the hammer. The other cast on'the side of the extension 21. A torsion spring 1| coiled about the projecting end of the valve pin 64 inside of the arm 61 bears at one end against a lug 12 on the extension shown in Fig. 1.

thumb of either of the operatorshands. Thus,

when the operator is gripping the yoke with his right hand at the natural place of balance of the hammer, that is, adjacent the extension 21 as shown in Fig. 1, theright thumb is free to depress the knob 68 or allow it to rise under .the action of the spring N. All positions of the actuating. arm down to the fully open position shown in dotted outline in Fig. may be maintained conveniently by the operator's thumb without in any way disturbing the operators grip on the tool. As a result, the valve can be moved to regulate the air flow while the tool is being moved back and forth across the work as is the practice in straightening a work piece.

It is sometimes desirable to support the hammer in a vise and move a work piece back and forth between the die members with the pneumatic actuator operating. 'To do this, it is only necessary to disengage the spring 'H- from the lug 12. Then, the arm 61 will, with the yoke portion l4 disposed generally horizontally, fall by gravity to open position, thereby causing normal actuation of the die members.

Provision is made for causing the lower die member H to bound away from the under side of the work under each impact of the plunger 45 of the upper die member |3, thereby relieving the frictional drag of the die members on the work so as to permit the hammer to be moved easily back and forth-across the work. At the same time, this bounding movement is controlled in magnitude and so synchronized with the' movements of the plunger that the lower die member will always be forced back against the work before the next blow is struck by the plunger. This important action is obtained by properly proportioning the relative weights cf the pressure, actuated parts as well as the effective pressure areas of the piston 20 and the plunger 45. In the present instance, the piston 20 is approximately one inch in diameter while the diameters of the pistons 46 and 41 are one and one-quarter and one and three-eighths inches respectively. Thus, during the retracting or upward stroke of the plunger, the piston 20 has a substantiallygreater effective pressure area than the plunger 45, the pressure areaof the latter being determined by the difierences in the diameters of the pistons 46 and 41. On the down or active stroke, when the air pressure is exerted on the upper end of the plunger, the efiective pressure area is greater than that of the piston 20.- Thecup l3 and plunger 45 weigh six and eleven ounces respectively while the piston 20 andthe lower die member H carried thereby weigh approximately one pound. The

parts thus proportioned will, under air pressure of sixty-five pounds per square inch or'over, operate in the desired manner, the lower diemember rebounding from the work a distance of approximately one-sixty-fourth of an inch. In ad-, dition, the return of the lower die memberinto contact with the work and the striking of the next blow by the plunger 45 are so timed that while the lower die member is always positioned against the work so as to back the latter when a blow is struck, the period of contact is relatively short. As a result, the hammer exerts very little frictional drag on the Work and the operator may easily move-the tool across the work while gripping it with one hand only as Such accurat timing of the active movements of the plunger and the bound-- ing,of the lower die member avoids any possibility of a blow being struck when the work is not backed by the lower die and thus prevents denting of the work which might otherwise I occur.

By interconnecting the cylinders I 9, 43, and

44 through the tubular yoke and by making the effective pressure area of the piston 20 greater than that of the plunger 45 on the up or inactive stroke of the latter, the lower die will always be raised into contact with the work before the plunger is actuated to strike a blow. That is to say, the piston 20 will be raised under a pressure in the yoke lower than that required to raise the plunger due to the difference in the eifective areas of the pistons 46 and. As a result, th initial plunger movement will occur only after a pressure build up in the yoke .and the cylinders I9, 43, and 44 following raising of the lower die.

Preparatory to straightening a piece of sheet metal such for example as .the fender of a vehicle, the operator usually grips the hammer with oneor both hands. As illustrated in Fig. l, the fingers of one hand are extended around the underside of the yoke arm l4 adjacent the tubular extension 21 but leaving the thumb of the latter hand free to depress the knob 58 of the valve arm. With the valve closed, the lower die will be separated by gravity from the upper die as shown in dotted outline in Fig. 5. The work may easily be brought endwise in between th dies. When the latter are located on opposite sides of the portion of the work to be straightened, the arm. '61 is depressed and the valve opened to admit air simultaneously to the tube 10 and the cylinders I9, 43, and 44. This first raises the piston 20 to force the lower die against the work and the latter against the upper die l3. Then, the pressure builds up sufiiciently to actuate the plunger 45. The pressure is first effective on the under side of the piston 41 to raise the plunger as previously described. Then, after the piston 41 uncovers the groove 53, the full pressure is applied to the upper end of this piston and the plunger is projected downwardly to strike a sharp blow on the upper die member. The blow is transmitted to the work and the lower die member without noticeable movement of the cup l3. The plunger reciprocates extremely rapidly and any irregularities in the work are hammered out 'efiectually by the substantially flat surface of one die coacting with the curved surface of the other. Difierent areas of the work are covered by moving the dies across the work usually by sidewise motion of the yoke. This may be accomplished easily and even by one hand only because of the small friction drag which, as previously described, results from limiting the downward bounding of the 'lower die and properly timing its rebound. So rapid and effective is the hammering action that badly bent 'metal of, heavy gage such as is used in truck permit the hardened head 49 to constitute the upper die member and act directly on the work.

The plunger blow thus acts over a smaller work area and is accordingly more effective.

Lubrication of the lower piston 20 may b effected simply and conveniently by removing the piston from the cylinder l9 and placing a body of solid lubricant such as grease 15 in the upturned end ll of the yoke. The vibration to which the hammer is subjected in service operation causes this grease to creep upwardly along the inner wall of the tube into the cylinder l9 and be distributed efiectually over the piston walls. This action is aided by bending the lower end of the yokeas described and joining the cylinder l9 and tube so that their inner walls form a substantially continuous surface.

To lubricate the pistons 46 and 41, the die cup I3 is removed and the plunger is permitted to fall below its normal position to one in which the piston 46 is disposed below an oil hole 16 in the tube 26. Lubricating fluid is introduced through this hole and since it comes in between the pistons, both of the latter are lubricated effectually.

I claim as my invention:

1. In a pneumatic hammer of the character described, the combination of a die head, a yoke, and ajoint connecting one end of said yoke and said head to prevent loosening of the joint under the vibration encountered in service use of the hammer, said joint comprising a tubular extension on said head and adapted to receive the end of said yoke, said extension being slotted longitudinally at its end, an abutment within said extension for limiting the entry movement of said yoke end, ears on said extension disposed on opposite sides of the slot therein, a clamping bolt extending through said ears and said slot and having a transverse groove therein adapted to register with the said slot in one angular position of the bolt, and a projection on said yoke end adapted to move through said slot and groove and to be engaged by said bolt upon turning of the latter out of alinement with said slot, said bolt when tightened serving to contract said extension about said yoke end and acting on said projection to urge the yoke end against said abutment.

2. In a pneumatic hammer of the character described, the combination of a die head, a yoke, and a joint connecting one end of said yoke and said head to prevent loosening of the joint under the vibration encountered in service use of the hammer, said joint comprising a split tubular ex-' tension on said head and adapted to receive the end of said yoke, an abutment within said extension for limiting the entry movement of said yoke end, a projection on said yoke end, and a clamping bolt on said head adapted when turned to engage said projection and urge said yoke end against said abutment and when tightened to contract said extension about said yoke end.

3. In a pneumatic hammer of the character described, the combination of a casing having a cylinder therein open at opposite ends, a piston reciprocable in said cylinder, 9. die member at one end of said cylinder actuated by said piston,

the end of said casing and closing said cylinder,

the other disk fitting snugly within the cylinder beyond said recess, an expansible member between said disks projecting into said recess, and a screw device connecting said disks and clamping the disks against the casing and said member respectively.

4. In a pneumatic hammer oi the character described, the combination of a casing having a cylinder therein open at opposite ends, a piston reciprocable in said cylinder, a die at one end of said cylinder projected therebeyond by -said piston, and means closing the other end or the cylinder comprising a member disposed within but removable from said other end and projecting inwardly from the wall of said cylinder, a disk abutting against the end of said casing and closing said cylinder, and means including a screw device acting against said member and clamping said disk against the casing end.

5. A pneumatic hammer having, in combination, a single piece tubular yoke substantially straight at one end, means on the other end of said yoke providing a, cylinder communicating with the yoke, a piston reciprocable in said cylinder and supporting a lower die member, an inarm carried by said valve element exteriorly of said head and depressible by the thumb of the operators hand grasping said projection to support the yoke, a piston reciprocable in said second cylinder, and an upper die member actuated by said last mentioned piston.

6. A pneumatic hammer having, in combination, a single piece tubular yoke substantially straight at one end, means on the other end of said yoke providing a cylinder communicating with the yoke, a piston reciprocable in said cylinder, a lower die member actuated by said piston, a head providing a cylinder alined with said first cylinder and a lateral tubular projection telescoping with said straight yoke end,'said head having a fluid supply passage leading thereinto, a valve having an element movably mounted on said head and operableto establish communication within said head from said passage to said yoke and to 

